Why my first RAG layer starts in Postgres, not in a standalone vector database

When people say they are "adding RAG" to a workflow, the conversation often jumps too quickly to infrastructure choices. Should this use a vector database? Should there be a reranker? Should everything go into a knowledge graph? Those are valid questions, but they are usually not the first question. The first question is narrower: What approved knowledge should the workflow be allowed to retrieve before an AI decision happens? That is why my first retrieval layer for operational AI workflows starts in Postgres, not in a standalone vector database. The Workflow Problem In operations-heavy systems, the model usually should not answer from raw memory or from a giant prompt dump. The useful context already exists somewhere else: approved response rules; handoff criteria; product or service notes; source or campaign guidance; operational decisions that were already made by humans. The hard part is not generating fluent text. The hard part is retrieving the right approved context, showing which source influenced the decision and refusing when no safe source exists. Why Postgres First For this kind of workflow, most of the surrounding data is already relational: leads or conversations; workflow names; stages and owners; human review outcomes; source metadata; trace logs; document versions. So the first technical choice is not "where do vectors live in the abstract?" It is: Where can I keep retrieval close to the operational data model? Where can I log the retrieval path and the final decision together? Where can I evolve the schema without creating a second system too early? Postgres plus pgvector is a good first answer to that set of questions. It lets me keep: documents and chunks; metadata such as allowed use and approval requirements; retrieval traces; cost estimates; human review outcomes in one place. What The First Version Needs The first version does not need to be broad. It needs to be inspectable. My narrow retrieval scope looks like this: approved response rules